1. Field of the Invention
This invention relates to a method for preparing a golf ball by enclosing a ball body, which may be either a single or multi-layer solid core or a wound ball core, with a resin layer. More particularly, it relates to a method for preparing a golf ball of quality which ensures that a very thin resin layer is effectively formed around the ball to a uniform thickness.
2. Prior Art
In general, golf balls are classified into two categories, solid golf balls and wound golf balls. The solid golf balls include one-piece solid golf balls consisting of a single layer, two-piece solid golf balls having a solid core and a cover, and multi-piece solid golf balls having a solid core and a cover at least one of which has a plurality of layers. The wound golf balls have a solid or liquid center, thread rubber wound thereon, and a cover. If desired, these balls on the surface are further coated with a paint layer.
Whether it is of the two- or multi-piece solid golf ball or the wound golf ball, the cover is conventionally formed by an injection molding technique, namely by placing the core in a mold and injection molding a molten resin into the space between the core and the mold cavity. Also as a general rule, the paint layer is formed by spray coating.
Formation of a cover layer by injection molding, however, has several problems. The cover layer as injection molded is not fully uniform. Especially when the cover is a two-layer structure including an outer thin cover resin layer, it is difficult to produce such a thin cover resin layer uniformly by injection molding. More particularly, the core is placed at the center of the mold cavity to define a space between the core and the mold cavity inner surface for forming a cover. However, it is very difficult to maintain a thin and uniform cover-forming space around the core. Depending on the rheology of a molten resin to form a cover, the molten resin cannot fully penetrate to a narrower section of the cover-forming space. The resulting cover resin layer is not fully thin and uniform, but often contains thickness variations and defects such as holes.
The step of spraying and otherwise coating paint to golf balls is generally a finishing treatment at the last stage after dimple embossing. Sometimes, the paint layer can degrade the precision of dimples on the golf ball surface.